Some coaxial cables, typically referred to as hard line coaxial cables, include a center conductor constructed of a smooth-walled or corrugated, metallic (e.g., copper, aluminum, steel, copper clad aluminum, etc.) tube, the material selection depending on weight, cost, flexibility, etc. Such a center conductor is referred to herein as a tubular center conductor.
A tubular center conductor typically includes a hollow internal portion. Electrical connections to the tubular center conductor may be made within the hollow internal portion, because the electromagnetic signals within the coaxial cable pass using mainly the outer diametral portions of the tubular center conductor. Accordingly, coaxial cable connectors that are designed to work with such hard line coaxial cables typically include contacts that are extended within the hollow internal portion of the tubular center conductor. Such coaxial cable connectors are referred to herein as hard line connectors.
The contacts used in many of these hard line connectors are held against the hollow internal portion by a support arm. Each of these contacts is located at or near an end of the support arm, which is cantilevered from a mounting position within the hard line connector. During installation, each of these support arms, along with its respective contact, is deflected to a smaller effective diameter during installation into the hollow internal portion. The amount of deflection may vary greatly.
Each support arm is designed with a limit of elastic deflection that allows an amount of elastic deflection before the support arm is plastically deformed. The limit of elastic deflection accounts for a range of possible variations occurring within a single tubular center conductor or between different tubular center conductors. These variations are typically small, and may include manufacturing tolerances and design variations. When a tubular center conductor is corrugated, though, the variations within a single tubular center conductor or between different tubular center conductors can be significantly large. The limit of elastic deflection is less able to allow for significantly large variations. It has been observed that many of these significantly large variations cause the support arms to deflect beyond their limits of elastic deflection and become plastically deformed during installation. Once the support arm is plastically deformed, it will not return to its original position after a deflection.
Any plastic deformation of the support arms may result in a poor electrical connection between the contacts and the hollow internal portion of the tubular center conductor. As described above, each contact may be held against the hollow internal portion by a respective support arm. An amount of pressure applied by each contact is determined by the amount of elastic deflection between a free-state position of each support arm and an installed-state position of the support arm. Accordingly, any amount of plastic deformation of the support arm during installation will result in a reduced free-state position and, therefore, a reduced pressure applied by each contact.
Previous attempts have been made to increase the amount of elastic deflection available to each support arm by reducing the cross sectional thickness of the support arm. This reduction in the cross sectional thickness naturally allows for greater elastic deflections before the support arm becomes plastically deformed. It is important to note, however, that this reduction in the cross sectional thickness correspondingly reduces the amount of pressure applied to the contact. Any reduction in, or elimination of the amount of pressure applied to the contact may reduce the quality of the connection and degrade the signal.
Other attempts have been made to increase the amount of pressure applied to the contact by various methods, such as increasing the cross sectional thickness of each support arm and using more resilient materials. This increase in the amount of pressure comes with a strong disadvantage of increasing an amount of moving force required to install the contact assembly into the hollow internal portion of the tubular center conductor. This increased installation force may result in damaged contacts and/or an incomplete installation. Both of these outcomes may reduce the quality of the connection and degrade the signal.
The quality of the electrical connection between the contacts and the hollow internal portion of the tubular center conductor can also be affected by the axial variation of the points of contact. While the helical corrugations provide structural stability during bending of the coaxial cable and the tubular center conductor, the helical corrugations also provide a non-regular surface against which the contacts make contact. Particularly with 1¼ inch or 1⅝ inch cables, but also with other sized helical and/or corrugated cables, one or more contacts around the radius of the center tubular conductor are likely to contact the center tubular conductor at different axial locations along the length of the contact. For instance, one contact might contact the center tubular conductor at a first end of the respective contact, while another contact, or portion of the same contact, might contact the center tubular conductor at a second end of the respective contact opposite the first end in the axial direction. The contact that contacts the center tubular conductor at the second end of the contact can produce an undesirable RF effect on the performance of the connector. A “hanging” reverse path for RF propagation is created, which acts like a resonating stub. This effect can reduce the overall transmission efficiency of the connector, and result in the appearance of a periodic phantom high and low impedance downstream of the contact when viewing the connector and the coaxial cable in a time domain.